Date of Award

Summer 2012

Document Type


Degree Name

Doctor of Philosophy (PhD)


Aerospace Engineering

Committee Director

Robert L. Ash

Committee Member

Ali Beskok

Committee Member

Ayodeji Demuren

Committee Member

Duc T. Nguyen


This study was undertaken to investigate the influence of pressure relaxation on steady, incompressible flows with strong streamline curvature. In the early part of this dissertation research, the significance of non-equilibrium pressure forces in controlling the structure of a steady, two dimensional axial vortex was demonstrated. In order to extend the study of pressure relaxation influences on more complex rotating flows, this dissertation has examined other rotating flow features that can be associated with hurricanes, tornadoes and dust devils. To model these flows, modified boundary layer equations were developed for a fluid column rotating near a solid plane including the influence of non-equilibrium pressure forces. The far-field boundary conditions were inferred using the asymptotic behavior of the governing equations, and the boundary conditions for the axial and radial components of velocity were shown to be dependent on the pressure relaxation coefficient, η p, and the characteristic angular velocity of the rotating fluid column, ω. This research has shown for the first time that the inclusion of non-equilibrium pressure results in a free-standing stagnation plane at the top of a funnel shaped rotating fluid column, which is consistent with observational data for hurricanes, tornadoes and dust devils. It has also been shown that in the absence of non-equilibrium pressure, the stagnation plane for rotating flows cannot be observed. The velocity and pressure distributions resulting from incorporating non-equilibrium pressure effects were then compared with available observational data for tornadoes and dust devils. The general profiles of the velocity and pressure distributions were found to be in good agreement with physical measurements, which was not possible without introducing empirical turbulence effects, in the absence of non-equilibrium pressure effects.